The present invention relates to a zoom lens system with a high zoom ratio.
Japanese Laid-Open Patent Publication No. H07-311340 discloses a compact zoom lens that includes wide-angle focal lengths, has a zoom ratio of around 3× or more, and favorably corrects various types of aberration. The publication discloses a zoom lens system in which a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, a fourth lens group with positive refractive power, and a fifth lens group with positive refractive power are disposed, where zooming is carried out from the wide-angle end to the telephoto end by moving the first lens group, the third lens group, the fourth lens group, and the fifth lens group toward the object, and, when a focal length of the second lens group is expressed as f2, a combined focal length of the entire zoom lens at the wide-angle end is expressed as fw, the combined focal length of the first lens group and the second lens group at the telephoto end is expressed as fT12, and a focal length of the entire zoom lens at the telephoto end is expressed as fT, where the conditions (−0.8<f2/fw<−0.5) and (−0.7<fT12/fT<−0.3) are satisfied.
In applications such as a digital video camera used for teleconferencing and security purposes, there is demand for a zoom lens that is bright, compact, and has high performance.